Wednesday, 17 January 2007: 4:30 PM
Handling convection and turbulence for weather and climate models .... Can one size fit all? (Invited)
206B (Henry B. Gonzalez Convention Center)
Numerical Prediction Models of grid sizes from 10 to 200 km with modest vertical resolutions from 10 to 100 layers typically utilize parameterization schemes to simulate the effects of convective clouds and boundary layer and clear air turbulence. This is done because these elements of the atmosphere exert significant influences on the evolution of the weather but are too small for the models to resolve them properly. For weather models, the emphases have been on the proper simulations of daytime boundary layers and the convective precipitations during warm seasons. In recent years, the ability to resolve meso-scale convective systems adds to the tasks of the parameterization schemes. For climate models, the feedback of the convective system to the global circulation on time scales of months and years has been the emphases of the modelers.
As the resolutions of the climate model increases, the demand of the parameterization schemes to handle demands from both weather and climate emerges. At NCEP, we are looking into the possibility to create/maintain parameterization schemes to handle both the weather and the climate requirements with an eye also toward the even higher resolution models when cumulus convection may be directly resolved. We will discuss our effort to handle all aspects of the demand and, yet, to keep the schemes as simple as possible to suit the operational efficiency requirement. Our goal is to come up with a simple set of parameterization schemes which will handle the forecast demands of both the seasonal predictions of climate means and the 1-2 day predictions of weather elements and to smoothly merge into the world of explicitly resolved convection and perhaps PBL turbulence.